Method of sealing a quartz tube

ABSTRACT

A method of deforming a quartz glass tube by means of plasma burners directed onto the place to be deformed. The quality and the rate of deformation are improved and shortened, respectively, by applying between the plasma burners and (alternating) voltage and contacting the resulting arc with the body to be deformed.

Einramhof et a1.

[ Dec. 3, 1974 METHOD or SEALING A QUARTZ TUBE Inventors: Franz Einramhof; Leonardus l-lenricus Adrianus Theresia Van Kronenburg; Ghislain Felix Alfons Arthur Verboven, all of Emmasingel, Eindhove Netherlands Assignee: U.S. Phillips Corporation, New

' York, NY.

Filed: Apr. 10, 1973 Appl. NQI 349,793

Related US. Application Data Continuation of Ser. No. 131,601, April 6, 1971, abandoned.

us. C1 65/34, 65/40, 65/70,

[56] References Cited UNITED STATES PATENTS 2,496,303 2/1950 Morse et a1 65/56 2,694,273 11/1954 Spyut 65/40 2,867,948 l/l959 Zimmerman... 65/40 3,264,508 8/1966 Lai et a1 315/1 1 l X 3,459,376 8/1969 Haase et a1. 315/111 X 3,684,474 8/1972 Chisholm 65/113 X Primary Examiner-Robert L. Lindsay, Jr. Attorney, Agent, or Firm-Frank R. Trifari 5 7] ABSTRACT A method of deforming a quartz glass tube by means of plasma burners directed onto the place to be deformed. The quality and the rate of deformation are improved and shortened, respectively,'by applying between the plasma burners and (alternating) voltage and contacting the resulting arc with the body to be deformed.

5 Claims, 2 Drawing Figures 65/105, 65/113, 65/DIG. 4 Int. Cl. C03b 21/02, C03b 33/06 Field of Search 65/34, 40, 56, 70, 105, 65/112,ll3,138,139,155, DIG. 4; 316/19; 315/111 PATENTEL-BEB 31914 f 3852.053

INVENTORS FRANZ EINRAMHOF LEONARDUS HA.TH. VAN KRONENBURG GHISLAIN F.A.A. VERBOVEN METHOD OF SEALING A QUARTZ TUBE tion are not completely desirable, inter alia, because.

holes are easily formed in the body.

The present invention avoids these drawbacks and is characterized in that in prior art the method as described above an electrical conductor, preferably one that is cooled, is placed opposite the plasma burner and an electric voltage is applied between the burner and the conductor so that a secondary arc is formed and the body to be deformed is located in the secondary arc.

It is found that as compared with the quality of the deformation advantages are obtained, for example, a shorter time of deformation, if, according to an embodiment of the invention, the conductor opposite the plasma burner is also a plasma burner whose radiation is also directed onto the body to be deformed and one of the angles between the center lines of the two plasma I The axes of the two plasma burners are not in the elongation of each other; one of the angles between the axes is smaller than 180 (see FIG. 2).

As soon as the two plasma burners 7 and 8 are ignited and the arc 11 is formed, the plasma burners 7, 8 and the lamp vessel 1 are together moved downwards. Since the exhaust tube 5 is held in the device 6, the strongly heated part of the exhaust tube 5 is reduced in area which finally becomes a wire and is ultimately sealed. The downward movement of the burners 7, 8 and the lamp vessel is continued until the exhaust tube 5 is severed at the sealed region. As a result of the arc 11, the sealing time becomes shorter and the quality both of the sealing tip and of the sealed lamp is improved as compared with the so far used method without an arc, while the possibility of holes in the exhaust tube is eliminated. 4

In a given lamp having a diameter of 12 mm and an exhaust tube diameter of 4 mm, an alternating voltage of 40 volts was set up between the burners; the current was 200 amperes. Argon was used as the gas in the plasma burners. The overall sealing time was 2 seconds.

It is not necessary that two plasma burners be present since one burner is sometimes enough. Instead of the second burner a member is used which moves with the lamp and the first burner and between which member and the first burner the arc is ignited.

a quartz glass body, which device is suitable for carrying out the above-described method, and a lamp vessel whose exhaust tube is sealed according to the new method.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawing, which shows diagrammatically a device for carrying out the method and which is to be considered as an example of said method.

In the drawing, FIG. 1 is a side elevation of a device having two plasma burners and an arc for sealing a tube of a quartz lamp, and

P16. 2 is a plan view of the device shown in FIG. 1.

Reference numeral 1 in the figures denotes a lamp vessel of quartz glass which comprises a pinch 2 having lead-in members 3 and a filament 4. An exhaust tube 5 through which the lamp vessel 1 is evacuated and then filled with a gas, is sealed to the lamp vessel, or housing, 1 and on its upper side is clamped in a device 6 which also seals the exhaust tube 5.

Two plasma burners 7 and 8, whose plasma radiations 9 and 10, respectively, are directed onto the place where the exhaust tube 5 is to be sealed, are present on either side of the exhaust tube 5 at approximately the height of the place where the exhaust tube 5 is secured to the lamp vessel 1. I

A plasma burner is to be understood to mean in this connection a discharge device in which a jet of superheated, partly ionized gaswhich is in an excitedcondition flows out of the nozzle. Between the two plasma burners, an electricvoltage is set up so that an arc 11 is formed. The tube 5 is in the path of said are 11.

When two plasma burners are used, however, it is found that the arc is more stable and does not extinguish which extinguishment may occur sometimes when one burner is used.

By using the plasma arc it is found that an additional electric field is formed by which the shape of the plasma flame can be varied. This shape can be varied as a result of which the flame can be adapted to the purpose for which it is destined.

The embodiment of the invention described may be used in all cases in which a quartz glass body is to be deformed, in which it has been found that both the time required for the deformation is reduced and the quality of the deformed body is improved.

What is claimed is:

1. A method of deforming a quartz glass body, comprising:

a. providing a plasma burner and an electrical concluctor, said electrical conductor being disposed opposite said plasma burner and said plasma burner being adapted to emit plasma radiation;

b. applying an electric voltage between said plasma burner and said electrical conductor so that a secondary arc is formed therebetween, said secondary arc envelops at least a portion of said quartz body and said plasma radiation of said plasma burner being directed onto said quartz glass body; and

c. deforming said body so as to seal said glass body at said portion thereof and to sever said portion.

2. A method as defined in claim 1, wherein said conductor is a second plasma burner adapted to emit second plasma radiation, said second plasma radiation being directed onto said quartz glass body at the portion thereof impinged by said plasma radiation of said plasma burner, the center lines of said plasma burner and of said second plasma burner defining an angle less than so as-to minimize a pressure increase in the area between said'burners, thereby enhancing electrical contact between said burners.

3. A method as defined in claim 1, wherein said conductor is cooled during said method of deforming said quartz glass body.

4. A method as defined in claim 1, wherein said uated and filled with gas, said exhaust tube being heated and deformed so as to be sealed.

5. A method as defined in claim 1, comprising evacuating said lamp vessel and filling said lamp vessel with quartz glass body comprises a lamp vessel and an ex- 5 gas before the step of deforming said quartz glass body.

haust tube through which said lamp vessel can be evac- 

1. A method of deforming a quartz glass body, comprising: a. providing a plasma burner and an electrical conductor, said electrical conductor being disposed opposite said plasma burner and said plasma burner being adapted to emit plasma radiation; b. applying an electric voltage between said plasma burner and said electrical conductor so that a secondary arc is formed therebetween, said secondary arc envelops at least a portion of said quartz body and said plasma radiation of said plasma burner being directed onto said quartz glass body; and c. deforming said body so as to seal said glass body at said portion thereof and to sever said portion.
 2. A method as defined in claim 1, wherein said conductor is a second plasma burner adapted to emit second plasma radiation, said second plasma radiation being directed onto said quartz glass body at the portion thereof impinged by said plasma radiation of said plasma burner, the center lines of said plasma burner and of said second plasma burner defining an angle less than 180* so as to minimize a pressure increase in the area between said burners, thereby enhancing electrical contact between said burners.
 3. A method as defined in claim 1, wherein said conductor is cooled during said method of deforming said quartz glass body.
 4. A method as defined in claim 1, wherein said quartz glasS body comprises a lamp vessel and an exhaust tube through which said lamp vessel can be evacuated and filled with gas, said exhaust tube being heated and deformed so as to be sealed.
 5. A method as defined in claim 1, comprising evacuating said lamp vessel and filling said lamp vessel with gas before the step of deforming said quartz glass body. 